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Figure 10 – Basic screen layout
First of all we set up our replication parameters.
Dim replicator As New SqlCeReplication
replicator.InternetUrl = interneturl
replicator.Publisher = publisher_server
replicator.PublisherDatabase = publisher_database
replicator.PublisherSecurityMode = publisher_secmode
replicator.Publication = publication
replicator.Subscriber = subscriber
replicator.SubscriberConnectionString = connection_string
Table 2 explains the settings for replication.
Table 2 – Replication parameters
Name |
Description |
InternetURL |
SQL Server CE communicates with a SQL Server Agent (sscesa20.dll) running on the desktop computer by means of HTTP. IIS on the desktop computer has been configured to accept SQL Server CE requests and forward them to SQL Server by using the SQL Server Agent. The InternetURL property specifies the URL that has been configured for this purpose. In this example, the value is http://192.168.1.25 /Northwind/sscesa20.dll.
You will need to replace 192.168.1.25 with the IP address of your server running IIS. Refer to Figures 7 and 9 for verification.
|
Publisher |
The Publisher property identifies the instance of SQL Server publishing the publication in the form machineName\SQLServerInstanceName. In this example, the value is delldesktop. |
PublisherDatabase |
The PublisherDatabase is the Sql Server database we are using for Replication. In this example, it is Northwind |
PublisherSecurityMode |
The PublisherSecurityMode determines whether the subscriber application will use NT authentication (as in our sample), or PublisherLogin and PublisherPassword entries e.g. ‘sa’ and ‘admin’. |
Publication |
This identifies the subscribing device or computer. |
Subscriber |
This identifies the subscribing device or computer. This example uses DNS.Gethostname() to send the name of the device. |
SubscriberConnectionString |
This specifies the connection string for the local ‘northwind’ database, and is used both in replication, and in accessing the local database. |
Next we attempt to connect to the IIS system, and create our local copy of ‘northwind’, by using AddSubscription
If Not System.IO.File.Exists(local_database) Then
Try
replicator.AddSubscription(AddOption.CreateDatabase)
Catch ex As Exception
Cursor.Current = Cursors.Default
DisplaySQLCeErrors(ex, "Add")
End Try
End If
After we have created the database, we then attempt to populate it with the data from our publication (our ‘northwind’ SQL Server database).
Try
replicator.Synchronize()
Cursor.Current = Cursors.Default
MessageBox.Show("Database synched with Server", "Finished")
Open_Local_Database()
Refresh_Grid()
Catch ex As Exception
Cursor.Current = Cursors.Default
DisplaySQLCeErrors(ex, "Synch")
End Try
If this is successful, we display a message, as shown in Figure 11, otherwise we display the error collection, in the same way we did in the SQLCLIEN sample.
Figure 11 – Successful creation and replication.
We then open the local database, and display the regions in a grid control as show in figure 12.
Figure 12 – Records displayed from local database after replication.
Our application so far has connected to our IIS server, created a local database, and populated it. We will now move on to adding records to our local database, and replicating these back to our SQL Server. The code behind the Add Region button, will bring up a data-entry form, allowing us to enter a new region and description. Our data entry form will also do some validation, to ensure the fields are filled in correctly, and we are not trying to add a duplicate entry.
strSql = "Insert into region (regionid,regiondescription) values ("
strSql += txtID.Text & ",'" & txtRegion.Text & "')"
SqlCmd = New SqlCeCommand
SqlCmd = sqlCeConn.CreateCommand
SqlCmd.CommandText = strSql
Try
SqlCmd.ExecuteNonQuery()
SqlCmd = Nothing
Catch ex As SqlCeException
DisplaySQLCeErrors(ex, strSql)
End Try
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